This proposal is designed to evaluate the relationship between the pharmacokinetics and cardiovascular effects of organic nitrates administered intravenously and orally to man. The pharmacokinetics will be related to the responses observed during cardiac catheterization, echocardiography, and exercise testing. Plasma concentrations of trinitroglycerin and isosorbide dinitrate will be determined by gas chromatography and compared to an enzymatic assay being developed in our laboratory.